Continuous monoculture often induces soil salinization, leading to degradation of several soil chemical and biological properties and reduced crop resilience, thereby challenging the sustainability of intensive vegetable production. Here, we evaluated whether synthetic microbial consortia integrated with a biochar-vinegar matrix could serve as a strategy with potential for low-input application to alleviate salinity stress and enhance cucumber performance in continuous cropping soil under controlled greenhouse conditions. The combined amendment was associated with improved soil physicochemical properties, including soil pH a ∼0.5 units increase in pH, a ∼25%, reduction in electrical conductivity, and reductions in Cl– and HCO3– of 20–30%, relative to Mock. Time-course analysis revealed that sustained ion reduction required viable microbes. Microbial incorporation reshaped soil communities, increasing bacterial and actinomycete composition by 30–40% while suppressing fungal proliferation by ∼25%. Compared with single-strain inoculations, microbial consortia produced more consistent growth promotion, including enhancing shoot and root biomass by 35–45%, improving leaf gas exchange parameters by ∼20%. In parallel, antioxidant defense systems were activated, with POD, CAT and APX activities elevated by 25–40% and oxidative stress indicators (PPO) reduced by 20–30%. Collectively, these results indicate that biochar-vinegar-supported microbial consortia are associated with a coordinated recovery of soil chemical properties, microbial community structure, and plant physiological resilience. This integrated, biologically driven strategy may serve as a promising option pending filed validation for restoring soil health and enhancing crop performance in salinity-affected continuous cropping systems.

Heat stress increasingly threatens global agriculture by disrupting photosynthesis and cellular redox homeostasis in plants. Spermidine (Spd), a stress-responsive polyamine, enhances thermotolerance by bolstering antioxidant capacity and stabilizing membranes; however, the molecular mechanisms underlying these effects remain incompletely characterized. Here, we demonstrate that Respiratory burst oxidase homolog 1 (RBOH1) is essential for Spd-induced thermotolerance in tomato (Solanum lycopersicum L.). Deficiency of RBOH1 compromised the protective effects of Spd, resulting in exacerbated membrane damage and a pronounced decline in photosynthetic performance under heat stress. Although Spd upregulated RBOH1 expression, the absence of RBOH1 disrupted Calvin cycle activity and impaired antioxidant modulation. Consequently, Spd-induced improvements in CO2 assimilation and redox homeostasis were abolished in rboh1 mutants. Our findings identify RBOH1 as a central molecular link integrating Spd signaling with photosynthetic protection and redox regulation, revealing a critical polyamine-RBOH1 axis that not only advances the mechanistic understanding of thermotolerance but also provides actionable insights for breeding heat-resilient crops.

Transglutaminases (TGases) are multifunctional enzymes involved in stress responses, while autophagy is a key cellular degradation process. However, the relationship between TGases and autophagy in the plant heat stress response remains poorly understood. In this study, we demonstrated that TGase was essential for heat tolerance by regulating autophagy. Heat stress induced both TGase expression and activity. The tgase mutants reduced, while TGase-overexpression (TGaseOE) lines increased plant thermotolerance. Under heat stress, insoluble proteins were more ubiquitinated in tgase mutants and less so in TGaseOE plants. Moreover, TGase promoted the expression of autophagy-related (ATG) genes and autophagosome formation. Polyamine content and the expression of polyamine-related genes, particularly SAMS2, were positively correlated with TGase activity. TGase interacted with SAMS2 both in vitro and in vivo, and knockout of SAMS2 impaired TGase-induced thermotolerance and autophagosome formation in TGaseOE plants. Exogenous spermidine also promoted autophagosome formation in tgase mutants, indicating a critical role of polyamine in TGase-mediated heat tolerance and autophagosome formation. Furthermore, a cell-free degradation assay showed that TGase enhanced the stability of SAMS2. Altogether, these results reveal that TGase interacts with and stabilizes SAMS2 to promote polyamine synthesis, which upregulates ATG gene expression and facilitates autophagosome formation to degrade ubiquitinated proteins, thereby enhancing the thermotolerance of tomato plants.

Heat shock transcription factors (Hsfs) and B-cell lymphoma2 (Bcl-2)-associated athanogene (BAG) proteins are essential for plant responses to high-temperature stress. Autophagy plays a crucial role in plant stress resistance by maintaining intracellular homeostasis. However, the mechanisms by which BAG proteins mediate Hsf-induced autophagy to enhance thermotolerance remain unclear. Here, we found that HsfA1a enhances tomato (Solanum lycopersicum L.) thermotolerance by inducing autophagy to degrade ubiquitinated proteins. HsfA1a directly binds to the BAG5b promoter to activate its expression and also interacts with BAG5b both in vitro and in vivo. The HsfA1a-BAG5b interaction enhances the HsfA1a-mediated transcriptional activation of BAG5b and the autophagy-related gene ATG10. BAG5b-overexpressing plants exhibited enhanced thermotolerance and increased autophagosome accumulation, whereas bag5b mutant plants were hypersensitive to high-temperature stress and showed inhibited autophagosome formation. Furthermore, knockout of BAG5b or ATG10 in HsfA1a-overexpressing plants compromised HsfA1a-induced thermotolerance and autophagosome formation. Taken together, our data reveal that HsfA1a promotes BAG5b expression by binding to its promoter under high-temperature stress. Subsequently, BAG5b interacts with HsfA1a to activate ATG10 expression, which promotes autophagosome formation to degrade ubiquitinated protein aggregates, ultimately enhancing tomato thermotolerance.

The heat shock transcription factors (Hsfs) and Bcl-2-associated athanogene (BAG) are crucial in response to heat stress. However, the relationship and regulation mechanism between Hsfs and BAGs in plants are largely unknown. Here, we demonstrated that the HsfA1a-BAG2 module mediated thermotolerance through regulating heat shock proteins (HSPs) in tomato. Overexpression of HsfA1a in tomato increased thermotolerance and enhanced the expression of HSP70, HSP90, and BAG2, but compromised in hsfa1a mutant plants. Yeast one-hybrid, dual luciferase, electrophoretic mobility shift assay, and chromatin immunoprecipitation coupled with qPCR assays found that HsfA1a directly bound to the promoter of BAG2 to activate its expression. BAG2 interacted with HsfA1a and BAG5b both in vitro and in vivo. Importantly, BAG5b facilitated the interaction between BAG2 and HsfA1a, resulting in enhanced transcriptional activation capacity of HsfA1a to HSP70 and HSP90. Either overexpression of BAG2 or BAG5b increased thermotolerance, concomitant with sustained expression levels of HSP70 and HSP90 genes. By contrast, knockout of BAG2 or BAG5b displayed the opposite results. Furthermore, silencing of BAG2 or BAG5b in HsfA1a overexpression plants attenuated HsfA1a-induced thermotolerance and HSPs expression. Thus, HsfA1a mediated thermotolerance through transcriptionally regulating BAG2 and forming a complex with BAG2 and BAG5b to ultimately induce the expression of HSPs in tomato. Our findings provide new insights into the regulatory network of Hsfs on HSPs under heat stress in plants.

Salt stress poses a significant challenge to plants, exerting a detrimental impact on crop growth and yield. This study investigated the effects of the strain Bacillus cereus on plant growth, ion contents and antioxidant metabolism of cucumber seedlings under salt stress (150 mM NaCl). The results showed that B. cereus could colonize the roots system of cucumber, with peak colonization occurring on the 3rd day. Inoculation with B. cereus effectively alleviated the growth inhibition of cucumber seedlings induced by salt stress, resulting in improvements in plant height, stem diameter, fresh and dry weight. Furthermore, the Na+ content in cucumber seedlings subjected to salt stress was significantly reduced by 38.35 % in leaves and 38.19 % in roots upon B. cereus inoculation, while K+ content increased by 9.88 % and 168.34 % in leaves and roots, respectively. Additionally, B. cereus significantly enhanced antioxidant enzyme activity and antioxidant content, while reduced the levels of H2O2, MDA, and O-2(-). in cucumber seedlings under salt stress conditions. B. cereus-treated seedlings exhibited an increase in soluble sugar content by 35.27 % and 93.21 % in leaves, and 59.36 % and 128.78 % in roots, respectively. Moreover, B. cereus treatment significantly up-regulated the expression of salt tolerant gene in both cucumber leaves and roots. These results showed that B. cereus enhanced salt tolerance in cucumber seedlings by modulating the antioxidant defense system, maintaining ion homeostasis, and promoting the expression of stress- related genes, ultimately improving the growth of cucumber seedlings.

High temperature is a significant abiotic stress that affects growth and development of plants. BAG (Bcl-2 associated athanogene) protein family members act as co-chaperones and apoptosis inhibitors in multiple cellular processes. BAG, MAPK (Mitogen-activated protein kinase), and programmed cell death (PCD) play critical roles in plant growth and development, stress response, and disease resistance. In this study, we investigated the interaction of BAG, and MAPK as well as their putative role in PCD under either short or long-term heat stress. We constructed mutants of bag2 and mapk2 in tomato using CRISPR/Cas9. Our results revealed that tomato BAG2 and MAPK2 interacted positively both in vivo and in vitro. In addition, after 3 h of heat stress, the activities of Caspase 3 and antioxidant enzymes, expression levels of Caspase 3 and Caspase 9, and contents of H2O2 in bag2 and mapk2 mutant plants were lower than those in WT (wild type) plants. Moreover, under short-term (3 h) heat stress, the DNA fragmentation phenomena and trypan blue coloration in both mutants were less severe than in WT plants; however, DNA integrities were broken, and the number of dead cells was higher under long-term (24 h) heat stress. Additionally, the electrolyte leakage was increased, but the Fv/Fm (maximum photochemical efficiency) value was decreased in mutants following exposure to heat stress. These results suggested that tomato BAG2 and MAPK2 suppressed short-time heat-induced PCD while promoting long-time heat-induced PCD.

The interior light environment in greenhouses affects the growth of crops. Researchers have extensively studied improvements in greenhouse light environments. In this article, computer technology was used based on light path tracing and the Monte Carlo method, and a light environment simulation model that is applicable to various greenhouses was developed. Two types of greenhouses with complex roofs were simulated: three-span doublelayer film greenhouses and multispan solar energy greenhouses. Experiments were performed to verify that the method could simulate the light environment distribution in greenhouses with various structures. The accuracy of the simulated average solar radiation intensity in greenhouses was greater than 85%, and the simulation correlation coefficient exceeded 0.90. Finally, by adjusting the ratio of rise to span of the greenhouse roof to optimize the greenhouse light environment, the greenhouse light distribution optimization results were found to be consistent between the two types of greenhouses, which verifies the effectiveness of the optimization. At three time points (9:00, 12:00, and 15:00), the horizontal section of the crop canopy (1.5 m) was simulated to construct a light distribution cloud map, and the point cloud data were statistically analyzed. The results show that the influence of the ratio of rise to span on the light distribution uniformity was more significant than that of the total radiation intensity. With an increasing the ratio of rise to span of the three-span double -film and multispan solar energy greenhouses, the total radiation intensity first increased and then decreased, and the light distribution uniformity showed a decreasing trend. When the ratio was 0.05, the total radiation intensity was high. Compared with that in the test greenhouse, the light intensity maximum increased by 6.95% and 6.64%, respectively, and the light distribution uniformity maximum increased by 14.49% and 14.74%, respectively. Combining the two factors of total radiation intensity and light distribution uniformity, the ratio of rise to span of these two types of greenhouses was maintained at 0.05. This design could ensure a greenhouse light distribution uniformity of approximately 90% based on the acquisition of the optimal amount of light energy, which is conducive for establishing a better greenhouse light environment. A statistical analysis of the total daily solar radiation throughout the winter season indicated that the application of the optimization scheme increased the total radiation in the three-span double -film and multispan solar energy greenhouse by 5.59% and 10.49%, respectively. The above results verified the effectiveness of the optimization. The greenhouse lighting simulation method based on optical path tracking is fast and accurate and could be used in greenhouse design and optimization.

The yellowing of leaves caused by the decomposition of chlorophyll (Chl) is a characteristic event during senescence, which can be induced by various environmental stresses. However, the molecular mechanisms of high temperature-induced Chl degradation in horticultural plants remain poorly understood. Here, we found that heat stress induced Chl degradation and the expression of ABI5 and MYB44 in cucumber. Silencing of ABI5 compromised heat stress-induced Chl degradation, and the transcription of pheophytinase (PPH) and pheophorbide a oxygenase (PAO), two key genes in Chl catabolic pathway, but silencing of MYB44 exhibited the opposite results. Furthermore, ABI5 interacted with MYB44 in vitro and in vivo. ABI5 positively regulated heat stress-induced Chl degradation through two pathways. ABI5 directly bound to PPH and PAO promoters to promote their expression, leading to accelerating Chl degradation. On the other hand, the interaction between ABI5 and MYB44 reduced the binding of MYB44 to PPH and PAO promoters and led to the ubiquitination-depended protein degradation of MYB44, thereby alleviating the transcription inhibitory effect of MYB44 on PPH and PAO. Taken together, our findings propose a new regulatory network for ABI5 in regulating heat stress-induced Chl degradation.

Greenhouses provide suitable environmental conditions for plant growth. Double-layer plastic greenhouses are often used in many regions to ensure normal crop growth during winter since single-layer plastic greenhouses have poor insulation. However, during summer, the high insulation of double-layer plastic greenhouses, combined with excessive external solar radiation, can cause high temperatures inside the greenhouse that are not suitable for plant growth and require cooling. In this study, we propose a double-layer spray greenhouse using a high-pressure spraying system that is placed inside the double film that allows for additional cooling capacity during the summer in order to sustain plant growth. A greenhouse platform test was set up to investigate the optimum operating conditions for the nozzles and to explore changes in greenhouse microclimate under different nozzle operating conditions. The results show that (1) the cooling rate increases with increasing water supply pressure, nozzle diameter and spraying time, and the humidification rate is consistent with the change in the rate of cooling. (2) The optimal condition for cooling in this experiment is achieved with a 120° double nozzle with a nozzle diameter of 0.30 mm, a water supply pressure of 6 MPa, and a spraying time of 15 min, which can reduce the temperature by up to 5.36 °C and serve as a reference for the summer cooling of the double-layer greenhouse.

S-adenosylmethionine (SAM), which is synthesized from methionine and ATP catalyzed by S-adenosylmethionine synthetase (SAMS), is an important methyl donor in plants. SAMS and DNA methylation play an important role in the plant response to abiotic stresses. Previous studies have shown that SAMS improves salt tolerance in tomato plants, but it is not clear whether the DNA methylation pathway mediates SAMS-induced salt tolerance. This study confirmed that SlSAMS1-overexpressing plants exhibited improved salt tolerance. Through whole-genome bisulfite sequencing (WGBS) and transcriptome sequencing (RNA-seq) analysis, the study screened the circadian rhythm pathway and identified the gene SlGI in this pathway, which was regulated by SlSAMS1. The gene body region of SlGI, the core gene of the circadian rhythm pathway, was hypermethylated in SlSAMS1-overexpressing plants, and its expression level was significantly increased. Furthermore, the SlGI-overexpressing plants showed higher salt tolerance, less reduction in plant height and fresh weight, lower electrolyte leakage, malondialdehyde and H2O2 content, and higher antioxidant enzyme activity compared to wild type plants. Therefore, SlSAMS1-overexpressing plants regulated significant changes in CHG-type methylation sites of the SlGI gene body and its expression levels, leading to an enhanced salt tolerance of tomato plants.

Previous studies have shown that spermidine (Spd) can improve tolerance to high temperature stress in tomato seedlings. To further understand how Spd regulates the molecular components of high temperature stress signaling pathways, we performed a genome-wide transcriptome analysis in tomato seedlings treated with high temperature and/or exogenous Spd. The results demonstrate that, under high temperature conditions, Spd significantly alleviated the inhibition of plant growth, as well as improving the net photosynthetic rate and pigment contents. The transcriptome analysis revealed thousands of differentially expressed genes (DEGs) in response to high temperature with or without Spd treatment. Half of the genes were induced by high temperature, part of the genes were induced by high temperature with exogenous Spd, and some were induced by the coordinated effect of high temperature and Spd. A GO analysis indicated that genes involved in cellular processes, metabolic processes, and nucleotide binding in the sample were subjected to high temperature. Some DEGs were also involved in plant physiological processes. These results suggest potential genes and molecular pathways were involved in the exogenous Spd-mediated tolerance to high temperature stress in tomato plants. A JA signaling test was designed, which indicated that MYC2 and JAS1 in heat-resistant materials were both increased, through quantitative RT-PCR.

Light environment research in greenhouses is mainly focused on solar greenhouses with simple structures; the universality of illumination models is low to date. To study the light environments in various of greenhouses, Greenhouse Light Environment Simulation software has been developed based on the ray tracing and Monte Carlo methods. The function of the software is to analyse the light path of the sampling point. The software has been verified and applied in a three-span plastic greenhouse. The results show that the mean relative errors of each month and typical weather conditions are less than 10%. The mean relative error of the simulated mean at any point in the greenhouse is less than 4%. The solar radiation intensity in the greenhouse is mainly affected by the solar incidence angle, and the solar radiation uniformity is mainly affected by the roof shape; the average solar radiation intensity in the greenhouse is the highest in August (over 250 W/m2), and the lowest in December, (below 60 W/m2). When the greenhouse is oriented at 10 degrees east by south, the total solar radiation is 2% higher and the uniformity of daily solar radiation is 0.8% higher than when the greenhouse is oriented to the south.

Soil salinization poses a huge challenge to the development of agriculture and seriously decreases crop yield and quality. In recent years, grafting has become one of the key agronomic techniques used to enhance plant abiotic stress tolerance. In this study, we found that watermelon [Citrullus lanatus (Thunb.) Matsum. & Nakai] grafted onto bottle gourd (Lagenaria siceraria Standl.) significantly enhanced salt tolerance. Transcriptome analysis revealed that a total of 8462 differentially expressed genes (DEGs) were identified, and the number of up- and down-regulated genes were 3207 and 5255, respectively. The DEGs in the bottle gourd rootstock-grafted plants were mainly involved in carbon metabolism, photosynthesis, and plant hormone signal transduction. Furthermore, proteome analysis identified 28 differently expressed proteins (DEPs) in bottle gourd rootstock-grafted plants under salt stress. These DEPs were closely associated with amino acid and protein synthesis, photosynthesis, mitochondrial metabolism and carbon metabolism, and stress defense. Combined transcriptome and proteome analyses showed that salt stress-responded genes in bottle gourd rootstock-grafted watermelon seedlings were mainly involved in plant hormone signal transduction, photosynthesis, and amino acid synthesis pathways.

Strigolactone is a new type of plant hormone, which has multiple roles in regulating the response of plants to environmental stress. However, the regulatory mechanism of strigolactone in hypocotyl elongation under low light stress is poorly unclear. Here, we studied the effects of light intensity and application of synthetic analog of strigolactone (GR24) concentrations on hypocotyl elongation in cucumber seedlings, and we investigated putative functions of strigolactone in suppressing low light-induced hypocotyl elongation in cucumber and its interaction with gibberellin, cytokinin, and abscisic acid. The results showed that application of 10 μM GR24 could reduce the hypocotyl length and the ratio of hypocotyl length to diameter of cucumber under low light stress. Under low light stress, GR24 modulated the expression of genes in the metabolic pathways of strigolactone, gibberellin, cytokinin and abscisic acid, thereby increasing the contents of endogenous strigolactone, abscisic acid and cytokinin, and decreasing endogenous gibberellin content in the cucumber hypocotyl. In addition, GR24 reduced the expression of the genes encoding for the cell elongation-regulating extensor expansion protein (EXP), xyloglucan endotransglucosylase (XET), tonoplast intrinsic protein (TIP) and telomerase binding protein SCAR3 in the hypocotyl of cucumber seedlings, thereby slowing down the hypocotyl cell elongation induced by low light stress. These results indicated that GR24 could affect the expression of cell elongation-related genes by regulating the metabolism of endogenous strigolactone, gibberellin, cytokinin and abscisic acid, thereby alleviating the hypocotyl elongation induced by low light stress.

As one of the key enzymes in the biosynthesis of polyamines, S-adenosylmethionine decarboxylase (SAMDC) plays an important role in plant stress resistance. In this study, four SAMDC genes (CsSAMDC1-4) were identified in cucumber (Cucumis sativus L.) and divided into three groups (I, II, and III) by phylogenetic analysis. Motif analysis suggested the existence of many conserved motifs, which is compatible with SAMDC protein classification. Gene structure analysis revealed that CsSAMDC2 and CsSAMDC3 in group I have no intron, which showed a similar response to salt stress by gene expression analysis. CsSAMDC3 responded differently to hormone and stress treatments, and was more susceptible to salt stress. Compared with wild-type (WT) tobacco, the activities of superoxide dismutase, peroxidase, and catalase were increased in CsSAMDC3-overexpressing tobacco under salt stress, but the content of electrolyte leakage, malondialdehyde, and hydrogen peroxide were decreased, which alleviated the inhibition of growth induced by salt stress. Under salt stress, overexpression of CsSAMDC3 in transgenic tobacco plants exhibited salt tolerance, mainly in the form of a significant increase in dry and fresh weight, the maximal quantum yield of PSII photochemistry, the net photosynthetic rate and the content of spermidine and spermine, while the content of putrescine was reduced. In addition, the expression levels of antioxidase-related coding genes (NtSOD, NtPOD, NtCAT) and PAs metabolism-related coding genes (NtSAMS, NtSPDS, NtSPMS, NtPAO) in transgentic plants was lower than WT under salt stress, which suggested that overexpression of CsSAMDC3 affected the expression of these genes. In summary, our results showed that CsSAMDC3 could be used as a potential candidate gene to improve salt tolerance of cucumber by regulating polyamine and antioxidant metabolism.

[Objectives]The purpose of this paper was to verify the application effect of special fermentation agent independently developed by the laboratory, and to form the biological fermentation process and fermentation technology system of mushroom residue. [Methods]Using mushroom residue as test material, five treatments of control（no fermentation agents）,the addition of 0.2%,0.5%,0.8%（m/m）self-developed special fermentation agents and 0.8% commercial fermentation agent were set up to explore the effect on the fermentation effect of mushroom dregs. The traditional and static flip-free composting fermentation methods were used to study the effects of different stacking methods on the temperature, physical and chemical properties and seed germination index of mushroom residue fermentation. [Results]The temperature of the reactor increased rapidly with the addition of 0.5% special fermentation agent, and pH value, electrical conductivity（EC）and organic matter contents reached a stable state before the control and commercial bacterial agent treatment, and the fermentation speed was fast. The highest temperature of mushroom residue was 73.8 ℃ in the addition of 0.5% special fermentation agent of flip-free composting fermentation method, which was 2.2 ℃ higher than that of traditional composting fermentation; the fermentation time was about 30 days, which was 5 days shorter than that of traditional composting fermentation; at the end of fermentation, the indexes such as organic matter and content E4/E6（fermentation maturity）reached a stable state earlier than that of traditional composting fermentation; the seed germination index reached 88.91%,which was 2.48% higher than that of traditional composting fermentation. [Conclusions]The fermentation time of mushroom residue can be shortened and the fermentation quality can be improved by adding special fermentation agents in two composting methods, while the fermentation efficiency and quality of mushroom residue can be further improved by static flip-free composting fermentation combined with the addition of 0.5% special fermentation agent.

The original intention of farmers adopting the vegetable-rice production system is to improve economic benefits and land use efficiency. However, the effects of the vegetable-rice rotation system on soil still need to be further clarified. This study explored the responses of different vegetable species-rice rotation systems to the trends of soil physio-chemical and enzyme activities for evaluating soil fertility level. Besides, the economic benefit was also used as an overall index for assessing the performance of various vegetable species-rice rotation systems. This study conducted two check treatments and five vegetable-rice production systems to assess the effects of rotation system on soil. The results showed that vegetable-rice cropping systems improved soil physico-chemistry characteristics. Meanwhile, vegetable-rice rotation systems enhanced alkaline N, Olsen P, and Olsen K during the vegetable growth period. Additionally, spinach-pakchoi-rice and spinach—rice systems could promote the decomposition and transformation of organic matter, the ability to transform alkaline N and Olsen P, and soil fertility due to the appropriate soil pH improved enzyme activity. Importantly, vegetable-rice system promoted rice yield increases by at least 405 kg ha−1. Meanwhile, vegetable-rice cropping systems significantly increased the net profit by more than 2.6-fold over the single rice system (USD3909–5928 ha−1). The improvement of the soil’s physical properties and enzyme activities during the vegetable growth could enhance the soil fertility of the paddy fields. The vegetable-rice system could improve soil fertility by optimizing soil physio-chemical characteristics and increasing enzyme activities, which helps keep the soil quality and sustainable.

Crops around the world are facing a diversity of environmental problems, of which high temperatures are proving to be the most serious threat to crops. Polyamine putrescine (Put) acts as a master growth regulator that contributes to optimal plant growth and development and increased stress tolerance. Here, the current study aimed to elucidate how Put functions in regulating chlorophyll (Chl) metabolism, oxidative stress, and antioxidant defense, as well as to characterize the expression of genes related to heat stress in tomato seedlings under such stress. The results revealed that Put treatment significantly attenuates heat-induced damage by promoting biomass production, increasing photosynthetic efficiency, and inhibiting excessive production of oxidative stress markers. Heat stress markedly decreased the Chl content in the tomato leaf and accelerated the leaf yellowing process. However, Put-treated tomato seedlings showed a higher Chl content, which could be associated with the functions of Put in elevating PBGD activity (Chl biosynthesis enzyme) and suppressing the activity of the Chl catabolic enzyme (Chlase and MDCase). Under high-temperature stress, the expression levels of the gene encoding factors involved in Chl biosynthesis and Chl catabolism were significantly down- and upregulated, respectively, and this trend was reversed in Put-treated heat-stressed seedlings. In addition, exogenous application of Put boosted the activity of antioxidant enzymes, along with the levels of expression of their encoding genes, only in plants that were heat stressed. Furthermore, the expression levels of heat-shock-related genes (HSP90, HSP70, and HsfA1) were elevated in Put-treated, high-temperature-stressed tomato seedlings. Taken together, our results indicate that Put treatment significantly increases the heat tolerance of tomato seedlings, by elevating Chl concentrations and suppressing Chl catabolic enzyme activity, modulating endogenous free PA content, increasing antioxidant defense efficiency, and upregulating the expression of heat-shock-related genes.

尖孢镰刀菌是番茄枯萎病的致病菌,该研究利用拟康宁木霉T-51菌株对尖孢镰刀菌展开对峙培养试验、防治最适温度、酸碱度筛选试验及生物防治效果试验,并测定防治试验中番茄幼苗叶片的生理生化指标和水杨酸、茉莉酸合成和信号途径关键基因表达量,探讨T-51菌株的生物防治机理.结果表明:(1)T-51菌株可显著抑制对峙培养中尖孢镰刀菌生长;随着环境温度和pH的增加,T-51菌株对尖孢镰刀菌的抑制率先升后降,并且在20℃、pH 7环境下效果最佳.(2)T-51菌株和尖孢镰刀菌混合孢子液处理番茄幼苗植株无明显的感病症状,植株生长状态与清水对照组无显著差异,枯萎病发病率和病情指数比单施尖孢镰刀菌孢子液处理显著大幅度降低,相对防效为87.5％.(3)与单施尖孢镰刀菌孢子液处理相比,混合孢子液处理番茄幼苗叶片的叶绿素荧光参数最大光化学效率、光化学淬灭系数和表观光合电子传递速率,以及抗氧化酶SOD、POD、CAT活性均显著增加,而非光化学淬灭系数和过氧化氢含量均显著降低.(4)与单施尖孢镰刀菌孢子液处理相比,混合孢子液处理番茄幼苗叶片的内源水杨酸(SA)显著降低,而茉莉酸(JA)含量显著升高,同时SA信号通路上的PR1和TGA2基因表达量均显著下调,JA合成基因LoxD的表达量显著上调.研究认为,拟康宁木霉T-51菌株对尖孢镰刀菌有显著的防治效果,并在20℃、pH 7环境下防治效果最佳;T-51菌株可能通过抑制尖孢镰刀菌侵染,增强番茄叶片抗氧化酶活性,提高叶片光合效率,以及调控水杨酸和茉莉酸合成和信号途径关键基因表达,调节内源水杨酸和茉莉酸含量,进而提高番茄植株的枯萎病抗病性.研究结果为番茄抗枯萎病提供了生防途径的理论依据.